# US 12,602,300 B2 · Techniques for efficiently transitioning object groups to low RPO replication mode

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- Number: US 12,602,300 B2
- Document ID: US12602300B2
- Status: Granted
- Kind: B2
- Application number: 18/778,087
- Filed: 2024-07-19
- Published: 2026-01-22
- Granted: 2026-04-14
- Earliest claimed: 2024-07-19
- Assignees: Dell Products L.P.
- Applicants: Dell Products L.P.
- Inventors: Prakash Venkatanarayanan; Girish Sheelvant; Sathya Krishna Murthy; Nagapraveen Veeravenkata Seela
- Web page: https://patentgrep.com/patent/US12602300B2

## CPC

- G06F 11/2074: {Asynchronous techniques}
- G06F 11/2094: {Redundant storage or storage space (G06F11/2056 takes precedence)}
- G06F 11/1451: {by selection of backup contents}
- G06F 11/2097: {maintaining the standby controller/processing unit updated (initialisation or re-synchronisation thereof G06F11/1658 and subgroups)}
- G06F 2201/83: the solution involving signatures
- G06F 2201/84: Using snapshots, i.e. a logical point-in-time copy of the data
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

Techniques can include: establishing an asynchronous replication configuration for a replication session of a source volume group VG1 and a target volume group VG2; and performing processing to transition the replication session to a low RPO (recovery point objective) replication mode comprising: setting the replication session to an alternative asynchronous replication (AAR) mode; transitioning the replication session to a hybrid mode; creating a first snapset of snapshots of source volumes of VG1; replicating each snapshot of the first snapset from a source to a target system in either the low RPO replication mode or the AAR mode based on an associated member level asynchronous replication mode corresponding to said each snapshot; and constructing a second snapset of snapshots of target volumes of VG2, wherein each snapshot in the second snapset denotes a same point in time copy as a corresponding snapshot in the first snapset.

## Claims

### Claim 1

A computer-implemented method comprising:
establishing an asynchronous replication configuration of a replication session associated with i) a source volume group VG1 of source volumes on a source system, ii) a target volume group VG2 of target volumes on a target system, and iii) volume pairs each including a source volume of VG1 and a unique corresponding target volume of VG2, wherein the source volume and the corresponding target volume of said each volume pair are configured for asynchronous replication such that writes to the source volume are asynchronously replicated to the corresponding target volume; and
performing first processing to transition the replication session to have a group level asynchronous replication mode denoting a low RPO (recovery point objective) replication mode comprising:
setting the group level asynchronous replication for the replication session to an alternative asynchronous replication (AAR) mode, wherein each source volume of VG1 has an associated member level asynchronous replication mode denoting the AAR mode;
transitioning the group level asynchronous replication mode of the replication session from the AAR mode to a hybrid mode, wherein i) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the AAR mode and ii) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the low RPO replication mode;
creating a first snapset of snapshots of the source volumes of VG1, wherein the first snapset is a group level snapshot of the source volumes of VG1 taken at a same point in time;
replicating each snapshot of the first snapset from the source system to the target system in either the low RPO replication mode or the AAR mode based on an associated member level asynchronous replication mode of a source volume of VG1 corresponding to said each snapshot; and
constructing a second snapset of snapshots of target volumes of VG2 on the target system, wherein each snapshot of a target volume of VG2 in the second snapset denotes a same point in time copy as a corresponding snapshot of a source volume of VG1 in the first snapset.

### Claim 2 (depends on 1)

The computer-implemented method of claim 1, wherein the first snapset and the second snapset serve as a common base of recovery snapshots.

### Claim 3 (depends on 1)

The computer-implemented method of claim 1, wherein a first volume pair SV1 of the replication session is configured from a first source volume SRC1 of VG1 and a first target volume TGT1 of VG2, wherein SRC1 has a first member level asynchronous replication mode denoting the low RPO replication mode and the first snapset includes a first snapshot SNAP1 of SRC1, and wherein said replicating includes:
replicating SNAP1, from the source system to the target system, in the low RPO replication mode using a low RPO replication technique.

### Claim 4 (depends on 3)

The computer-implemented method of claim 3, wherein SNAP1 denotes an Nth snapshot, SNAP N, of SRC1, and wherein SNAP N-1 and SNAP N denote successive snapshots of SRC1, and wherein said replicating SNAP1 using the low RPO replication technique includes:
determining a first delta set of changed content between successive snapshots SNAP N and SNAP N-1 of SRC1;
copying the first delta set of changed content from the source system to the target system;
applying the first delta set of changed content to TGT1; and
taking a snapshot SNAP2 of TGT1 after applying the first delta set.

### Claim 5 (depends on 4)

The computer-implemented method of claim 4, wherein SNAP2 is included in the second snapset, and wherein SNAP2 and SNAP1 denote identical point in time copies.

### Claim 6 (depends on 4)

The computer-implemented method of claim 4, wherein a first replication cycle or tracking session having a first tracking identifier ID1 is associated with SNAP N-1 and SNAP N of SRC1, the first member level asynchronous replication mode of SRC1 is the low RPO replication mode during the first replication cycle or tracking session, and the method includes:
tracking, in a write tracking cache, first locations of SRC1 that are associated with ID1 and written to during the first replication cycle or tracking session;
querying the write tracking cache for a list of tracked writes with a tracking identifier of ID1, wherein the list includes the first locations of SRC1 modified during the first replication cycle or tracking session;
reading, from a cache, first content written to the first locations of SRC1 during the first replication cycle or tracking session; and
copying the first content from the source system to the target system, wherein the first content is the first delta set of changed content applied to TGT1.

### Claim 7 (depends on 6)

The computer-implemented method of claim 6, wherein a log includes first records corresponding to: taking SNAP N-1 of SRC1, taking SNAP N of SRC1, and writing the first content to the first locations of SRC1.

### Claim 8 (depends on 7)

The computer-implemented method of claim 7, wherein the first records are retained in the log until the first content, written to the first locations of SRC1 during the first replication cycle or tracking session, has been copied from the source system to the target system; and wherein the first content is retained in the cache until the first content, written to the first locations of SRC1 during the first replication cycle or tracking session, has been copied from the source system to the target system.

### Claim 9 (depends on 8)

The computer-implemented method of claim 8, wherein responsive to copying the first content from the source system to the target system, third processing is performed including:
invalidating corresponding records of the log denoting said taking SNAP N-1 of SRC1 and said taking SNAP N of SRC1;
flushing one or more corresponding records of the log denoting the first locations of SRC1 written to during the first replication cycle or tracking session between SNAP N-1 and SNAP N; and
marking corresponding cache locations of the cache storing the first content indicating that the first content is allowed to be evicted from the corresponding cache locations.

### Claim 10 (depends on 1)

The computer-implemented method of claim 1, wherein a first volume pair SV1 of the replication session is configured from a first source volume SRC1 of VG1 and a first target volume TGT1 of VG2, wherein SRC1 has a first member level asynchronous replication mode denoting the AAR mode and the first snapset includes a first snapshot SNAP1 of SRC1, and wherein said replicating includes:
replicating SNAP1 from the source system to the target system in the AAR mode using an AAR technique.

### Claim 11 (depends on 10)

The computer-implemented method of claim 10, wherein SNAP1 denotes an Nth snapshot, SNAP N, of SRC1, and wherein SNAP N-1 and SNAP N denote successive snapshots of SRC1 of a first replication cycle, and wherein said replicating SNAP1 using the AAR technique includes:
determining a first delta set of changed content between successive snapshots SNAP N and SNAP N-1 of SRC1;
copying the first delta set of changed content from the source system to the target system;
applying the first delta set of changed content to TGT1; and
taking a snapshot SNAP2 of TGT1 after applying the first delta set.

### Claim 12 (depends on 11)

The computer-implemented method of claim 11, wherein SNAP2 is included in the second snapset, and wherein SNAP2 and SNAP1 denote identical point in time copies.

### Claim 13 (depends on 12)

The computer-implemented method of claim 12, wherein the first delta set includes first content denoting content written to first locations of SRC1 during the first replication cycle between SNAP N-1 and SNAP N, wherein a log includes first records corresponding to: taking SNAP N-1 of SRC1, taking SNAP N of SRC, and writing the first content to the first locations of SRC1.

### Claim 14 (depends on 13)

The computer-implemented method of claim 13, wherein the first content is not retained in a cache until the first content, written to the first locations of SRC1 during the first replication cycle or tracking session, has been copied from the source system to the target system, and wherein the method includes:
flushing the first records from the log before the first content, written to the first locations of SRC1 during the first replication cycle or tracking session, has been copied from the source system to the target system.

### Claim 15 (depends on 1)

The computer-implemented method of claim 1, wherein the first snapset is identified using a unique signature, and wherein said constructing the second snapset of snapshots of target volumes of VG2 on the target system includes:
identifying a first set of snapshots on the target system, wherein each snapshot of the first set has the unique signature, wherein the second snapset is the first set of snapshots having the unique signature.

### Claim 16 (depends on 1)

The computer-implemented method of claim 1, wherein the first processing includes, for each of the volume pairs of the replication session configured from a corresponding source volume and a corresponding target volume, performing second processing that individually transitions the corresponding member level asynchronous replication mode of said corresponding source volume of said each volume pair from the AAR mode to the low RPO replication mode, wherein said second processing includes:
taking a snapshot of the corresponding source volume;
replicating, in the AAR mode, the snapshot of the corresponding source volume from the source system to the target system;
determining an amount of changed content in the snapshot of the corresponding source volume; and
if the amount is less than or equal to a specified threshold, transitioning the corresponding member level asynchronous mode of the corresponding source volume of said each volume pair from the AAR mode to the low RPO replication mode.

### Claim 17 (depends on 16)

The computer-implemented method of claim 16, wherein said replicating, in the AAR mode, the snapshot of the corresponding source volume from the source system to the target system includes:
taking two successive snapshots of the corresponding source volume;
determining that first content is written to first locations of the corresponding source volume between points in time corresponding to the two successive snapshots;
copying the first content written to the target system; and
applying the first content to the first locations of a corresponding target volume.

### Claim 18 (depends on 1)

The computer-implemented method of claim 1, while the group level asynchronous replication mode of the replication session is the hybrid mode, the first processing includes:
taking group level snapshots of VG1 at defined fixed time intervals based on a defined RPO, wherein each of the group level snapshots of VG1 includes a first corresponding snapset of snapshots of the source volumes of VG1;
replicating the group level snapshots of VG1 from the source system to the target system; and
applying the group level snapshots of VG1 to VG2 to generate corresponding group level snapshots of V2, wherein each of the corresponding group level snapshots of VG2 includes a second corresponding snapset of snapshots of the target volumes of VG2.

### Claim 19

A system comprising:
one or more processors; and
a memory comprising code stored thereon that, when executed, performs a method comprising:
establishing an asynchronous replication configuration of a replication session associated with i) a source volume group VG1 of source volumes on a source system, ii) a target volume group VG2 of target volumes on a target system, and iii) volume pairs each including a source volume of VG1 and a unique corresponding target volume of VG2, wherein the source volume and the corresponding target volume of said each volume pair are configured for asynchronous replication such that writes to the source volume are asynchronously replicated to the corresponding target volume; and
performing first processing to transition the replication session to have a group level asynchronous replication mode denoting a low RPO (recovery point objective) replication mode comprising:
setting the group level asynchronous replication for the replication session to an alternative asynchronous replication (AAR) mode, wherein each source volume of VG1 has an associated member level asynchronous replication mode denoting the AAR mode;
transitioning the group level asynchronous replication mode of the replication session from the AAR mode to a hybrid mode, wherein i) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the AAR mode and ii) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the low RPO replication mode;
creating a first snapset of snapshots of the source volumes of VG1, wherein the first snapset is a group level snapshot of the source volumes of VG1 taken at a same point in time;
replicating each snapshot of the first snapset from the source system to the target system in either the low RPO replication mode or the AAR mode based on an associated member level asynchronous replication mode of a source volume of VG1 corresponding to said each snapshot; and
constructing a second snapset of snapshots of target volumes of VG2 on the target system, wherein each snapshot of a target volume of VG2 in the second snapset denotes a same point in time copy as a corresponding snapshot of a source volume of VG1 in the first snapset.

### Claim 20

A non-transitory computer-readable media comprising code stored thereon that, when executed, performs a method comprising:
establishing an asynchronous replication configuration of a replication session associated with i) a source volume group VG1 of source volumes on a source system, ii) a target volume group VG2 of target volumes on a target system, and iii) volume pairs each including a source volume of VG1 and a unique corresponding target volume of VG2, wherein the source volume and the corresponding target volume of said each volume pair are configured for asynchronous replication such that writes to the source volume are asynchronously replicated to the corresponding target volume; and
performing first processing to transition the replication session to have a group level asynchronous replication mode denoting a low RPO (recovery point objective) replication mode comprising:
setting the group level asynchronous replication for the replication session to an alternative asynchronous replication (AAR) mode, wherein each source volume of VG1 has an associated member level asynchronous replication mode denoting the AAR mode;
transitioning the group level asynchronous replication mode of the replication session from the AAR mode to a hybrid mode, wherein i) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the AAR mode and ii) at least one source volume of VG1 has a corresponding member level asynchronous replication mode of the low RPO replication mode;
creating a first snapset of snapshots of the source volumes of VG1, wherein the first snapset is a group level snapshot of the source volumes of VG1 taken at a same point in time;
replicating each snapshot of the first snapset from the source system to the target system in either the low RPO replication mode or the AAR mode based on an associated member level asynchronous replication mode of a source volume of VG1 corresponding to said each snapshot; and
constructing a second snapset of snapshots of target volumes of VG2 on the target system, wherein each snapshot of a target volume of VG2 in the second snapset denotes a same point in time copy as a corresponding snapshot of a source volume of VG1 in the first snapset.